My opinion, based upon nothing but misremembered comments here and talking to a couple of luthiers, is that the myth of Guilds being hard to reset is perpetuated by luthiers who lack the skill or the time to actually do the job.
When there are concrete reasons given there were times when more glue was used than absolutely necessary and so steaming the neck off takes longer than expected.
There are also stories that sometimes the glue pot was contaminated and so the neck is harder to get off with the usual techniques. I think of these stories as being Westerly and the '70's.
This is one of those cases where the utility of my post is in
encouraging people with better information to actually post in order to correct me
But there are definitely folks who have done resets themselves and don't think the Guilds are harder than any other brand.